Understanding and Calculating Head Pressure of a Pond Pump

Overview

To be able to select a suitable pump with correct specifications, including water flow rate, it’s crucial to understand the basics about pond pumps, including terms like Head Pressure, the amount of opposing force the water confronts while traveling from the pump to it’s release point. Head Pressure, is also known as Head Height, has to primary components. First is the influence from gravity which can easily be worked out if you know the vertical elevation from the pump to where the water achieves its highest point. Second is friction or chafing loss, induced by material contact between the water and plumbing as it journeys through the pump to its destination.

Calculating and combining these elements will give you a total Head Pressure equivalent for your system, and can help you to choose the suitable pump.

Calculating Head Pressure

Head Pressure is calculated and depicted in terms of feet (ft.) To be able to calculate the total Head Pressure of your plan, you have to figure out the difference in elevation between where the water is pumped from, to where the water is released. Additionally you need to plan the plumbing structure beforehand, such as all fittings and distances between tubes and/or pipes. The effects of gravity on head pressure is very simple; every vertical foot of distance the pump moves water equals one foot of head pressure (1:1 ratio). The effects of friction on head pressure is slightly more tough to calculate. Every ten feet of pipe through which water will travel leads to 1 foot of head height (10:1 ratio). Every 90 degree turn in your plumbing will lead 1 foot of head pressure (1:1 ratio). For example: if you are to install your pump 30 feet from the top of your waterfall, which was 4 feet above the pump, with two 90 degree elbows in your plumbing, your water feature’s head height would be 9 feet (plumbing distance contributes 3 ft, the vertical height contributes 4 ft, and the 90 degree turns contribute 2 feet). In this scenario, you would want to choose a pump that has the desired GPH rating at 9 feet of head pressure.

Tubing size is also a critical factor in accounting for head pressure loss, usually you should never lessen the diameter of the tubing below what the output size of the pump is, this will considerably raise head pressure, and decrease pump performance. For greatest pump performance, using the largest tubing that is practical is the best option. In-line filters and Ultraviolet sterilizers will also add significant head pressure, and several feet of head pressure will need to be added to make up.

Choosing A Pump

After you have worked out the total Head Pressure for your pond, you will next need to figure out the desired turnover rate, or Flow Rate for your water feature or pond that you a choosing a pump for. For example; If you have established that your desired flow rate is 1000 gph, and you have calculated that your total head pressure is 10ft, the smallest pump that will meet your needs is a pump that is rated for 1000gph @ 10 ft of head pressure, this will be a pump that has a maximum gph rating much higher than 1000 gph. Most manufacturers have a flow chart to be referenced with their pumps, as each pump is different. These charts may also tell the shut-off pressure, which is the maximum Head Pressure the pump can handle before it will no longer be able to generate flow. Be sure to reference these charts when selecting your pond pump to ensure the right choice for your design.

It’s also smart to select a pump that is larger than what your minimum requirements actually are, to allow for other factors that could additionally lower pump performance.